1. Technical Field
The disclosure relates to an optical fiber, an optical transmission system, and a method for measuring the optical fiber.
2. Related Art
Along with the dramatic increase of the Internet traffic in recent years, there has been predicted the lack of prospective transmission capacity. As a method to overcome this situation, in addition to a fundamental propagation mode of an optical fiber used conventionally, there has been disclosed a mode division multiplexing transmission technique in which a higher-order propagation mode is used for optical transmission (see C. Koebele, M. Salsi, G. Charlet, S. Bigo “Nonlinear Effects in Long-Haul Transmission over Bimodal Optical Fiber,” ECOC2010, Mo.2.C.6; and Bernd Franz, Detlef Suikat, Roman Dischler, Fred Buchali, Henning Buelow “High Speed OFDM Data Transmission Over 5 km GI-Multimode Fiber Using Spatial Multiplexing With 2×4 MIMO Processing,” ECOC2010, Tu.3.C.4). Furthermore, it is important for higher quality optical transmission to enlarge an effective core area (Aeff) of the optical fiber so as to suppress the occurrence of nonlinear optical phenomena in the optical fiber (see Marianne Bigot-Astruc, Frans Gooijer, Nelly Montaigne, Pierre Sillard, “Trench-Assisted Profiles for Large-Effective-Area Single-Mode Fibers,” ECOC2008, Mo.4.B.1; and Yoshinori Yamamoto, Masaaki Hirano, Kazuya Kuwahara, Takashi Sasaki “OSNR-Enhancing Pure-Silica-Core Fiber with Large Effective Area and Low Attenuation,” OFC/NFOEC2010, OTuI2).
However, when the effective core area of the optical fiber is enlarged, a bending loss becomes large. Particularly, when the fundamental and higher-order propagation modes of the optical fiber are used for optical transmission, the above-described bending loss occurs with respect to each propagation mode.
Accordingly, there is a need to provide an optical fiber, an optical transmission system, and a method for measuring the optical fiber in which even when the fundamental and higher-order propagation modes of the optical fiber are used for the optical transmission, the effective core area is large and the bending loss is small in each propagation mode.